Step chain plug-in axle

ABSTRACT

A step chain is provided for a person conveying device having a first strand, a second strand, a plurality of connecting axles and an attachment apparatus for detachably attaching the connecting axles to the first and second strands.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to people moving devices in general, and moreparticularly to people moving devices which employ a step chain.

2. Background Art

Escalators are a known method for conveying people from a firstelevation to a second elevation. Typically, an escalator includes aframe, a drive, a step chain and a pair of balustrade assemblies. Theframe comprises a truss section on both the left and right hand sides ofthe frame. By convention, the side of the escalator on the left of aperson facing the escalator at the lower elevation is called the lefthand side of the escalator, and the side to the person's right is calledthe right hand side. Each truss section has two end sections parallel toone another, connected by an inclined midsection. The end sections formlandings at the two elevations connected by the midsection, one on eachend. Matching pairs of roller tracks are attached on the inside of eachtruss section, i.e. the side of the truss section facing the other trusssection.

The escalator drive is attached to the frame in the upper landing,between the trusses. The drive typically drives a step chain sprocketassembly consisting of a pair of step chain sprockets, a pair ofhandrail sprockets, and an axle extending from one side of the frame tothe other. The two step chain sprockets power a step chain formed in aloop running from the first elevation to the second elevation.

The step chain consists of a pair of chain strands, having a pluralityof rollers, and a plurality of connecting axles for connecting the twochain strands. Each strand is formed from a plurality of chain links.Each link has a pair of side plates, an axle, and a roller. The axle isreceived in the center of the roller. A side plate of the link and aside plate of the next link in line, are attached to the axle on bothsides of the roller, thereby holding the roller and axle together. Thislink arrangement is repeated as many times as is necessary to arrive atthe length strand, and therefore the length chain, desired.

Every "n^(th) " link in the strand is connected to the aligned strand onthe other side of the frame. Connecting the axles together ties the twoindependent strands into a single step chain. One strand of the stepchain rides a roller track on the right side of the frame and the otherstrand rides the matching roller track on the left hand side of theframe. Each pair of connected rollers provides the support for one treadplate.

The rollers may be connected in a number of different ways. First, it isknown in the art for the aligned rollers to share a common axle. Thecommon axle extends through the two aligned links, acting as a singleaxle for the aligned rollers. Another method incorporates strands havingaligned stub axles which extend out a specific distance toward the otherstrand. In a first embodiment, a tread plate receives each stub axle ina bore on that side of the tread plate, thereby connecting the alignedstub axles. In a second embodiment, a connecting axle independent of thetread plate receives the aligned stub axles. The stub axles are pressfit into bores on the ends of the connecting axle and the tread plate isattached to the connecting axle. In a third embodiment, the tread platesare directly attached to the stub axles. A connecting axle, independentof the tread plate, receives the aligned stub axles on the inside of thetread plate. Holes are drilled in the connecting axle and the stub axlesto receive pins. The pins fix the connecting axles to the stub axles.

All of these methods of connecting the aligned rollers have distinctdisadvantages, however. First, step chains having a common axle betweenaligned rollers have a fixed width and therefore cannot be readilyinterchanged between different width escalators. Moreover, if a commonaxle becomes damaged, both strands must be disassembled to repair thechain.

Second, using stub axles connected by tread plates alone creates anundesirable loading on the roller bearing. The yoke of the tread plateattaches to the unsupported stub axle outside of the centerline of theroller bearing thereby creating a cantilever type arrangement. As aresult, the roller bearing experiences not only a load, but a moment aswell. The combination of load and moment create an undesirable stress onthe roller bearings which negatively effects the B¹⁰ life of thebearings. Increased maintenance frequency on an escalator seriouslydiminishes the desirability and quality reputation of the escalator.

In the case of the press fit connecting axle, the disadvantage lies inthe difficulty of assembling and disassembling the step chain in thefactory and especially in the field. To get the proper press fit, theconnecting axle and the stub axles must either be forced together or theconnecting axles must be heated and sweated onto the stub axles. Eitherway, the process is time consuming and difficult to disassemble in thefield.

Finally, attaching the tread plate to the stub axles and pinning theconnecting axle to the stub axle is also disadvantageous. Pinning theconnecting axle necessitates holes being drilled either at assembly orduring the manufacturing of the separate pieces. In the former case,drilling every connecting axle at assembly is a labor intensive and timeconsuming function. In the latter case, alignment of the bores must beprecise or an interference will occur. The potential for undesirableerror, either way, is present during the assembly process.

DISCLOSURE OF THE INVENTION

It is, therefore, an object of the present invention to provide aninexpensive, easy to manufacture and repair step chain that requiresminimal maintenance.

According to the present invention, a step chain is provided for apeople carrying device having a first strand, a second strand, aplurality of connecting axles and an attachment means for detachablyattaching the connecting axles to the first and second strands.

An advantage of the present invention is that it loads the bearings ofthe chain strands like a beam, instead of a cantilever, and thereforeeliminates the moment on the roller bearing, consequently, increasingthe life of the bearing.

A further advantage of the present invention is that it permits the stepchain to be readily assembled or disassembled. As a result, the stepchain is less expensive to ship, easier to handle and readily assembledor repaired.

A still further advantage of the present invention is that the readilyreplaceable connecting axles may be made in different lengths toaccommodate different width tread plates.

These and other objects, features and advantages of the presentinvention will become more apparent in light of the detailed descriptionof the best mode embodiment thereof, as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an escalator with broken away sectionsshowing details.

FIG. 2 is a sectional view of a step chain.

FIG. 3 is a diagrammatic view of part of a step chain link showing anembodiment of the attachment means.

FIG. 4 is a diagrammatic view of part of a step chain link showing anembodiment of the attachment means.

BEST MODE FOR CARRYING THE INVENTION

Referring to FIG. 1, an escalator is shown having a frame 10, a drive12, a plurality of tread plates 14 attached to a step chain 16, and apair of balustrades 18 for guiding a pair of handrails 20. Byconvention, escalators are said to have a left 22 and a right 24 hand.The left 22 and right 24 hands are determined by standing at a lowerfirst elevation 30 of the escalator and facing the escalator.

The frame 10 typically consists of a weldment of structural steelangularly extending from a first elevation 30 to a second elevation 32.The frame 10 includes pairs of matching roller tracks (not shown) fixedto the frame. One half of each pair is fixed to the left hand side 22 ofthe frame 10 and the other half to the right side of the frame 24. Theframe 10 also forms the structural basis for a landing on eachelevation. Hence, the frame 10 begins with a lower landing 28 at a firstelevation 30, then angularly extends upward via an inclined midsection31 to a second elevation 32, where it meets an upper landing 34. Theupper landing 34 typically provides the support for the drive 12 used topower the handrails 20 and the step chain 16.

Referring to FIG. 2, in the center of the frame 12 (not shown), betweenthe balustrades 18 (not shown), the step chain 16 follows a circuitouspath which allows it to draw the attached tread plates 14 either up ordown the inclined midsection 31 between elevations. The step chain 16comprises a left 38 and a right strand 40 and a plurality of connectingaxles 42. The left 38 and right 40 strands are left and right handversions of the same strand. The strands 38,40 comprise a plurality oflinks 44 pivotally attached to one another. Each link 44 has a pair ofside plates 46, an axle 48, and a bearing mounted roller 50. The axle 48is received in the center of the roller 50. A side plate 46 of the link44 and a side plate 46 of the link 44 next in line, are attached to theaxle 48 on both sides of the roller 50, thereby holding the roller 50and axle 48 together. The heretofore described link 44 arrangement isrepeated as many times as is necessary to arrive at the length chain 16desired.

Referring to FIGS. 2-4, every "n^(th) " link in the left 38 and right 40strands further comprises a cylindrical stub axle 52 which extendsoutside the side plate 46 on one side of the link 44. The stub axles 52of the left 38 and right 40 strands point toward the center of theescalator, and therefore toward one another. In a first embodiment, thestub axles 52 contain a ball bearing 54 (see FIG. 3) biased to extendpartially outside of the radial surface of the axle 52, as is known inthe art. In a second embodiment, the stub axles 52 have a radial groove56 (see FIG. 4) extending around the circumference of the stub axle 52.Snap rings 58 are provided which may be slidably received within theradial grooves 56.

In both embodiments, the aligned stub axles 52 are received within aconnecting axle 42. The connecting axles 42 may be a solid rod with abore 62 on each end or alternatively may be a tube. Either way theconnecting axles 42 further comprise a radial groove 64 on the innerdiameter of the tube or bore 62. In the first embodiment, inserting thestub axles 52 into the connecting axle forces the ball bearings 54radially inward toward the center of each stub axle 52. When a ballbearing 54 aligns with one of the radial grooves 64 in the innerdiameter of the connecting axle 42, the ball 54 extends radially outwardand into the groove 64, thereby preventing relative movement between thestub axle 52 and the connecting axle 42. The stub axle 52 and theconnecting axles 42 may be detached from one another by applying anaxial force. How much axial force must be applied depends upon themagnitude of the force biasing the ball bearing 54 radially outward.

In the second embodiment, inserting the stub axles 52 into theconnecting axle forces the snap rings 58 into the groove 56 in each stubaxle 52. When a snap ring 58 aligns with one of the radial grooves 64 inthe inner diameter of the connecting axle 42, the snap ring 58 extendsradially outward and into the groove 64 in the connecting axle 42,thereby preventing relative movement between the stub axle 52 and theconnecting axle 42. The stub axle 52 and the connecting axles 42 may bedetached from one another by applying an axial force. How much axialforce must be applied depends upon the magnitude of the force biasingthe snap ring 58 radially outward.

In both embodiments, the attachment means for attaching the connectingaxle 42 and the stub axle 52 is such that the connecting axle 42 and thestub axles 52 can be readily detached. Either strand of the chain,therefore, may be easily replaced as necessary. This is a decidedadvantage since it is more typical that one strand will wear out beforethe other.

On the other hand, the attachment means for attaching the connectingaxle 42 and the stub axle 52 may also be such that the connecting axle42 and the stub axles 52 cannot be readily detached. For example, thegeometry of the grooves 64 in the inner diameter of the connecting axle42 or the forces biasing the snap rings 58 or ball bearings 54 may bechosen such that the connecting axles 42 cannot be readily detached.Despite not being readily detachable, this configuration still enjoysease of assembly and improved loading on the roller bearings. Referringto FIG. 1, in a building having an escalator extending from a lowerfirst elevation 30 to a second higher elevation 32, the escalator frame10 is fixed to the first and second elevations by conventional means.The drive 12, located within the upper landing 34 on the secondelevation 32, drives a first step chain sprocket assembly 65. The chainsprocket assembly 65 includes a pair of step chain sprockets 66connected by an axle 68 extending across the width of the escalatorframe 10.

Between the two balustrades 18, the step chain sprockets 66 drive thestep chain 16 and attached tread plates 14 in a circuitous path from theupper landing 34 to the lower landing 28 and back. Because of thecircuitous path, tread plates 14 are always exposed in each landing28,34 and along the inclined midsection 31. A first roller track (notshown), one half on each side of the frame 10, guides and supports thestep chain 16. A second roller track (not shown), one half on each sideof the frame 10, supports a pair of rollers (not shown) attached to thebase of each tread plate 14.

The tread plates 14 enter the exposed portion of the step chain 16travel path aligned in a level surface, thereby forming a landing fromwhich a passenger may enter the escalator. Subsequently, as the treadplates 14 enter the inclined midsection 31, each tread plate 14 eitherraises or drops relative to the adjacent tread plate 14, depending onthe rotational direction of the escalator relative to the midsection. Asthe tread plates 14 enter the opposite landing, the incline or declinefades into a straightaway and the tread plates 14 again align into asingle flat surface. Subsequently, the step chain 16 and attached treadplates 14 revolve around a second step chain sprocket assembly 70 andreturn back, underneath the exposed tread plates 14 toward the firststep chain sprocket 66.

Referring to FIGS. 1 and 2, every link 44 in the step chain 16experiences a load by virtue of the chain sprockets 66 pulling orlowering the chain 16 up or down the midsection 31. The links 44 havingconnecting axles 42 also experience an individual load if a person orobject rests on the tread plate 14 attached to that particularconnecting axle 42. The loading on the connecting axle links may bedescribed as a pair of point loads supported by a beam. Specifically,the load is directly applied to the tread plate 14 and is, in turn,transferred to the connecting axle 42 via the yokes 72 of the treadplate 14. Each yoke 72 is fixed to the connecting axle 42 by a bushing74 slidably mounted on the connecting axle 42 and a pin (not shown)attached to the yoke 72. The yokes 72 receive the bushings 74 and thepins fix the yokes 72 to the bushings 74. The bushings 74, therefore,not only pivotly mount the tread plates 14 to the connecting axles 42,but also help distribute the load. The connecting axle 42 can thereforebe described as a beam supported on each end. The beam mounts, which arein this case the rollers 50 attached to the stub axles 52, in turntransfer the load to the roller tracks (not shown) attached to the frame10 of the escalator. No moments are created because the stub axles 52are not cantilevered. Roller bearings experiencing a radial load have alonger B-10 life than do roller bearings experiencing both a radial loadand a moment.

Although this invention has been shown and described with respect to thedetailed embodiments thereof, it will be understood by those skilled inthe art that various changes in form and detail thereof may be madewithout departing from the spirit and scope of the claimed invention.

We claim:
 1. A step chain for a person conveying device having aplurality of tread plates drawn along a predetermined path by said stepchain, comprising:a first strand, having a plurality stub axles; asecond strand, having a plurality of stub axles; a plurality ofconnecting axles, for supporting the tread plates which attach to thesaid connecting axles, wherein said stub axles of said first and secondstrands are received within and spaced apart by said connecting axles;and a plurality of snap rings, for attaching said connecting axles tosaid stub axles of said first and second strands, wherein each snap ringis received within a first groove in either of said stub axle or saidconnecting axle, such that when said stub axle is received within saidconnecting axle, said snap ring is biased into said first groove untilsaid first groove and a second groove in the other of said stub axle orsaid connecting axle are aligned, then said snap ring radially expandspartially out of said first groove and into said second groove, therebypreventing axial movement of said stub axle relative to said connectingaxle.
 2. A step chain for a person conveying device having a pluralityof tread plates drawn along a predetermined path by said step chain,comprising:a first strand, having a plurality stub axles; a secondstrand, having a plurality of stub axles; a plurality of connectingaxles, for supporting the tread plates which attach to the saidconnecting axles, wherein said stub axles of said first and secondstrands are received within and spaced apart by said connecting axles;and a plurality of ball bearings, received within one of said stub axleor said connecting axle and biased to extend partially outside of aradial surface of said axle, and a radial groove in the other of saidstub axle or said connecting axle, wherein when said stub axle isreceived within said inner diameter of said connecting axle, and saidball bearing aligns with said radial groove, said ball bearing extendsinto said groove, thereby preventing axial movement of said stub axlerelative to said connecting axle.
 3. A step chain for a person conveyingdevice having a plurality of tread plates drawn along a predeterminedpath by said step chain, comprising:a first strand, having a pluralityof stub axles; a second strand, having a plurality of stub axles; aplurality of connecting axles, for supporting the tread plate whichattach to the said connecting axles, wherein said stub axles of saidfirst and second strands are received within and spaced apart by saidconnecting axles; and a ball bearing, for detachably attaching saidconnecting axles to said stub axles of said first and second strands,said ball bearing received within one of said stub axle or saidconnecting axle and biased to extend partially outside of a radialsurface of said axle, and a radial groove in the other of said stub axleor said connecting axle, wherein when said stub axle is received withinsaid inner diameter of said connecting axle, and said ball bearingaligns with said radial groove, said ball bearing extends into saidgroove, thereby preventing axial movement of said stub axle relative tosaid connecting axle.
 4. A step chain for a person conveying devicehaving a plurality of tread plates drawn along a predetermined path bysaid step chain, comprising:a first strand, having a plurality stubaxles; a second strand, having a plurality of stub axles; a plurality ofconnecting axles, for supporting the tread plates which attach to thesaid connecting axles, wherein said stub axles of said first and secondstrands are received within and spaced apart by said connecting axles;and a snap ring, for detachably attaching said connecting axles to saidstub axles of said first and second strands, said snap ring receivedwithin a first groove in one of said stub axle or said connecting axle,and a second groove in the other of said stub axle or connecting axle,wherein when said stub axle is received within said connecting axle,said snap ring is forced radially biased into said first groove untilsaid first groove and said second groove are aligned, then said snapring radially expands partially out of said first groove and into saidsecond groove, thereby preventing axial movement of said stub axlerelative to said connecting axle.